Blood clot filters are used in combination with other thrombolytic agents to treat pulmonary embolism occurring within a patient. Such devices are generally inserted intravenously into a target location of the body (e.g. an artery or vein), and function by capturing blood clots (emboli) contained in the blood stream before they can reach the heart and/or lungs and cause permanent damage to the body. In the treatment of Deep Vein Thrombosis (DVT), for example, such filters are placed in the inferior vena cava to prevent further blood clotting in the large veins of the lower body. Placement of the filter is typically accomplished percutaneously via the femoral arteries or the jugular vein using a local anesthetic, or by performing a laparotomy with the patient under general anesthesia.
In certain designs, an introducer sheath may be used to deliver the blood clot filter through the body. Such introducer sheaths are generally tubular in shape, and include an inner lumen configured to transport the blood clot filter in a collapsed position through the body. Once transported to a desired location within the vasculature, the filter can then be removed from within the introducer sheath, allowing the filter to spring open and engage the vessel wall. A needle, hook, barb, prong, wedge or other attachment means disposed on the blood clot filter can be used to secure the filter to the vessel wall.
There are a number of situations in which it may be desirable for a physician to remove the filter once inserted within the body. In certain circumstances, for example, the risk of pulmonary embolism may be relatively short term (e.g. about two weeks), thus requiring insertion of the filter for only a short period of time. Permanent implantation of the filter in such cases may unnecessarily impede the flow of blood within the vessel, and can lead to further thrombosis growth at the filter implantation site. In other circumstances, it may be desirable to reposition the filter within the vessel, or to replace the existing filter with a new filter.